1. Field of the Invention
The present invention relates to an apparatus and method for fractionating a liquid sample, particularly a blood serum or plasma sample from which the low, very low, and ultra low density lipoproteins are to be removed.
2. Prior Art
It has recently been indicated that the level of high density lipoprotein cholesterol in a person's blood tends to be inversely related to the person's risk of coronary heart disease. Tests for high density lipoprotein cholesterol usually involve treatment of blood serum or plasma to remove the low, very low and ultra low density lipoproteins therefrom. This leaves the high density lipoprotein cholesterol in the serum or plasma sample, which may then be further treated for measurement of the high density lipoprotein cholesterol.
Measurements of high density lipoprotein in such samples are useful not only for study and prediction of coronary heart disease risk. Such measurements are also useful in conjunction with triglyceride and total cholesterol studies in the estimation of lipoprotein phenotypes.
To date, conventional techniques for effecting the separation of the low, very low and ultra low lipoprotein fractions from blood serum or plasma have involved centrifugation, frequently ultra centrifugation, electrophoresis, or high pressure liquid chromatography. Such prior art techniques have various disadvantages. Among the disadvantages are that relatively expensive equipment, apparatus or materials to effect separation have been required. The length of time necessary for performing separations, particularly in large scale testing laboratories, has frequently been inconveniently long. For example, the conventional centrifugation technique requires 30 to 45 minutes in the centrifuge. Further, the centrifuge should be of the expensive refrigerated type for good results. Finally, such prior art techniques have frequently required a sequence of steps such as pipetting, centrifugation and/or decanting which require care and skill of the technician performing the steps. Thus the disadvantages of prior art techniques have been that they are relatively slow and expensive and have required highly trained analysts and expensive equipment for their adequate performance.
As mentioned above, the importance of the relative amounts of high density and low density lipoprotein cholesterol as a diagnostic testing technique for detecting possible cardio-vascular problems, has been realized. Mass testing of patients on a regular basis, for these relative amounts is, thus, desirable. Yet, no inexpensive and rapid mass testing technique exists in the prior art for making the necessary analysis.
It is an object of the present invention to provide a rapid, simple and relatively inexpensive apparatus and method to achieve separation of the low, very low and ultra low lipoproteins from blood serum or plasma samples.
It is a further object of the present invention to provide such fractionated liquid samples ready for further analysis wherein any portion of a particular fractionated liquid sample may be analyzed to yield homogenous results.